Lecture 9 BIO 311D 2nd EditionOutline of Last Lecture I. Multiple selection factors working at once, including heterozygote advantageII. Evolution occurs in populations over timeOutline of Current Lecture I. Different Definitions of SpeciesII. How do new species form?Current LectureI. Different definitions of speciesA. Review- Macroevolution: new species are formed- Galapagos Finches serve as an example for microevolution and macroevolution Microevolution change in beak sizeMacroevolution adaptations (adaptive radiation)B. What’s a species? (How do we know when it is a “new” species?)- Morphological Species Concept: based on morphological, structural traits Fossil analysis is possibleUsed by Linnaeus to devise the species naming and classification system- Species are independent evolutionary unitsBiological species concept: groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups Disadvantages: doesn’t account for asexual organisms; fossil analysis aren’t possible; you can’t walk through an environment and notice new species through the biological species concept- The study of bacterial species asexual reproduction; bacteria can exchange genes throughthe plasma therefore should be studied through the morphological species concept combined with biochemical viewsII. How do new species form?A. Process of speciation: requires genetic divergence and reproductive isolation1. Genetic divergence: how fat apart are they from one another - Lack of gene flow, non-random mating, mutations, genetic drift, sexual selection, etc. B. Not all evolutionary changes result in new species- A species may change without giving rise to a new species or may transform into a new species- A speciation results from one species splitting into two species; each of which involves as a distinct lineageC. Modes of speciation1. Allopatric: divided by geographic barrier- Populations are separated- Lead to genetic divergence2. Sympatric: speciation without geographic barrier- Populations are together- Diverge genetically- Mutations that multiplies the chromosomes a polyploidy event: a genetic divergence thatcould possibly cause an instant reproductive isolation this is more common in
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